1. Field of the Invention
This invention relates generally to systems and methods for conditioning temperature of an enclosed space using a compressed fluid as a thermal energy transport and/or transfer medium.
2. Related Arts
In a conventional system for indoor climate control, such as, a Heating, Ventilating and Air Conditioning (HVAC) system, or a heat pump system, a network of air ducts are built into the walls/ceiling/floor of a building to circulate and/or re-circulate air inside the building. The network of air ducts is coupled to a furnace and/or a heat extraction unit, which actively adds or removes thermal energy of the air, depending on a target ambient temperature that needs to be achieved inside the building. The addition or removal of thermal energy to or from the air may take place in one of the following ways: 1) directly heating or cooling a flow of air that gets released inside the building; and, 2) heating or cooling a heat transfer fluid, and enabling thermal energy exchange between the flow of air and the heat transfer fluid. A combination of the above two methods is used too to increase the overall efficiency of the system. Conventionally, the flow of air that is circulated in the air ducts is at atmospheric pressure. If a heat transfer fluid is used, the flow of the heat transfer fluid is conventionally kept in a closed loop separate from the flow of air in the air duct, i.e. the heat transfer fluid does not get released inside the building.
Commonly used heat transfer fluids, such as, Freon, are not considered “green” or environmentally friendly. Though the heat transfer fluid does not get released inside the building, procurement and disposal of a non-green fluid adds to the carbon footprint of a system. Also, some amount of heat-transfer fluid may leak out from a closed loop to get mixed with the main air flow. If direct heating or cooling of a flow of air is adopted to avoid the use of a heat transfer fluid, then a relatively longer time and larger consumption of energy may be needed to achieve a target temperature.
Conventional systems for indoor climate control consume fossil fuel (for active heating) and/or electricity (both for active heating and cooling). Burning fossil fuel in a furnace directly produces air-polluting gases and residues locally, which need to be removed from the system. This adds to the operational cost and infrastructural requirements of the system. Electric-only heating and/or cooling systems do not rely on fossil fuels, but usually consume a large amount of electricity to generate or extract thermal energy, resulting in a high operational cost. The total carbon footprint of electric-only heating/cooling may be quite high, as most of the electric power plants still use fossil fuel to generate electricity.
What is needed is an efficient system for heating and cooling which is environmentally friendly, and consumes less electricity to achieve the same degree of temperature conditioning.